1. Field of the Invention
The present invention generally relates to a mold assembly for forming an ophthalmic lens, a method of producing the mold assembly, and a method of producing the ophthalmic lens by using the mold assembly. More particularly, the present invention is concerned with such a mold assembly for forming the ophthalmic lens such as a contact lens or an intraocular lens, which mold assembly does not suffer from undesirable deformation during a molding operation for forming the intended ophthalmic lens, to thereby permit easy and economical production of an ophthalmic lens having a desired configuration, and an advantageous method of producing such a mold assembly. Further, the invention is concerned with a method of producing the ophthalmic lens with the desired configuration at a relatively low cost, by using the mold assembly.
2. Discussion of the Related Art
There are proposed various techniques for producing an ophthalmic lens by a mold assembly consisting of a first mold and a second mold in the form of a male mold and a female mold, or an upper mold and a lower mold, which are assembled to define therebetween a mold cavity having a configuration that gives the intended ophthalmic lens such as a contact lens or an intraocular lens. The mold cavity defined upon closing of the first and second molds is filled with a suitable lens material to mold the intended ophthalmic lens.
JP-B-63-36484 and JP-B-3-1125 disclose a method of producing an ophthalmic lens by a molding operation, comprising the steps of assembling male and female molds together to define a mold cavity therebetween, introducing a polymeric material into the mold cavity, and polymerizing the polymeric material, to thereby provide the ophthalmic lens having an intended configuration. In the proposed method, the male and female molds are formed of a resin material rather than a metallic material, for assuring easy removal of the molded lens from the molds, and improved molding efficiency. In the male and female molds formed of the resin material, however, the surface conditions of the molding surfaces defining the mold cavity tend to vary during the molding operation. Moreover, the molds are easily deformed upon removal or releasing of the molded product therefrom, making it impossible to repeatedly use the molds in subsequent molding operations. Like ordinary resin products or articles, the resin-made male and female molds are generally produced by high-pressure molding such as injection molding, using metallic dies. The metallic dies used in the high-pressure molding need to have a high mechanical strength, and maintain the original surface condition which is sufficient to provide molding surfaces of the male and female molds with high accuracy of configuration, since the molding surfaces of the molds give the opposite surfaces of the ophthalmic lens to be obtained. Such high-pressure molding, however, undesirably and inevitably requires expensive equipment.
U.S. Pat. No. 5,524,419 discloses one example of a method and an apparatus for forming a contact lens by a molding operation, wherein a first and a second web each having a suitable width are continuously fed and subjected to a vacuum-forming operation for forming a succession of male molds in the form of posterior mold cavities in the first web, and a succession of female molds in the form of anterior mold cavities in the second web. These posterior and anterior mold cavities are formed in the first and second webs, respectively, such that the mold cavities are spaced apart from each other in the longitudinal direction of the first and second webs with a predetermined interval therebetween. After a predetermined amount of a curable lens material is introduced into each anterior mold cavity (as the female mold), the first and second webs are superposed on each other to close the male and female molds together. Thereafter, the lens material in the mold cavities between the male and female molds are polymerized by exposure to light, to thereby form the intended ophthalmic lens in each mold cavity. Subsequently, the first and second webs are separated from each other, and the contact lenses molded in the mold cavities are removed from the mold cavities.
In forming the male and female molds in the respective first and second webs by the vacuum-forming operation as disclosed in the above US Patent, the thickness of the webs in which the male and female molds are to be formed needs to be made small to a certain extent. If the thickness of the webs is relatively small, the male and female molds formed in the thin webs undesirably tend to be deformed during the molding operation for forming the contact lens. Accordingly, the contact lens molded in the deformed male and female molds may not have the intended optical characteristics.
JP-A-8-1673 discloses another example of the method and the apparatus for molding a soft contact lens by using a mold assembly which is produced by high-pressure molding such as injection molding using rigid metallic dies. In this method, the metallic dies need to have a high mechanical strength, and maintain a desired surface condition necessary to provide accurately shaped molding surfaces of the male and female molds of the mold assembly to be obtained by the metallic dies, since the molding surfaces of the male and female molds give the opposite surfaces of the soft contact lens to be obtained. Such high-pressure molding, however, undesirably and inevitably requires expensive equipment. In addition, since the male and female molds of the mold assembly obtained by the high-pressure molding as described above have a small wall thickness, the male and female molds are easily deformed during the molding operation for forming the soft contact lens. In this case, the soft contact lens molded in the deformed molds does not have the intended optical characteristics.